Alternating-current electromagnet.



D.L.' '1) T.

ALTERNATING GURR T "IROMAGNET. APPLICATION FILED Plum, 1910.

1,005,857, Patented 0ct.17,1911.

2 SHEETS-SHEET 1.

w/rfissw: (DINVENTOR I dad/ d .3 lah' I WW irronusr D. L. LINDQUIST.ALTEENATING CURRENT BLEGTROHAGNET.

APPLICATION FILED 1:23.11, 1910.

1,005,857. Patented 0ct;17,1911.

2 SHEETB-BHEBT 2.

J J i i 1 1 a a i WITNESSES: INVENTOI? 1 MATTORNEY UNITED STATES PATEN TOFFICE.

DAVID L. LINDQUIST, 0F YONKERS, NEW YORK, ASSIGNOR T0 OTIS ELEVATORCOMPANY, A CORPORATION OF NEW JERSEY.

ALTERNATING-CUBRENT ELECTROMAGN ET.

Specification of Letters Patent.

Patented Oct. 17, 1911.

Application filed February 9, 1910. Serial No. 542,818.

T 0 all whom it may concern:

Bev it known that I, DAvm L. LINDQUIST, a subject of the King of Sweden,residing at Yonkers, in the county of Westchester and State of New York,have invented a certain new and useful Improvement inAlternating-Current Electromagnets, of which the following is aspecification.

The invention is an alternating current electromagnet comprising a coreand primary and secondary conductors constructed and arranged so thatmagnetic fluxes different in phase are produced therein, whereby thetractive eifect on the armature never falls to zero, and hence aconstant pull is exerted which prevents chattering of said armatureagainst the core.

The invention consists in the proportioning of the secondary conductor,and in the construction of core and conductor, as more particularlypointed out in the claims.

In the accompanying drawings-Figure 1 is a side elevation of myalternating current magnet, showing the coil in section. Fig. 2 is asimilar View of a modified form in which the secondary conductor isplaced on the stationary instead of on the movable member of the core.Fig. 3 is a similar view of another modified form in which secondaryconductors are placed on both the secondary and movable members of thecore. Fig. 4 is a similar view of still another modified form in whichboth members of the core are movable, with a secondary conductor oneach. Fig. 5 is an enlarged section of the polar end of the movablecore, showing the convex extremity. Fig. 6 is a top view of saidextremity. Fig. 7 is an enlarged section of the polar end of the movablecore, showing two secondary circuit conductors therein. Fig. 8 is a topview of said extremity. Fig. S) shows a portion of the movable coreinclosing the secondary conductor, the said secondary conductor havingarms protruding frmn the core and connected to a member actuated by saidcore.

Similar letters of reference indicate like parts.

A is the statitmary core, B the movable core or armature, and C theprimary coil which is to be connected with any suitable source ofalternating current.

In the form of my device shown in Fig. 1, the secondary circuit is asleeve D of metal, which is seated in two recesses milled in the endofthe movable core O. The portion of the core surrounded by sleeve 1)has its end face F convex, as best shown in Figs. 5 and 6, and thisconvex extremity, when the core is in attracted position, meets theabutment formed by the stationary core, so that themovable core B isfree to rock on said extremity and thus to adjust itself symmetricallyin the magnetic field. In order to permit this, a slight clearance isleft at G between the core B and the ends of the arms of the field coreA. On each side of the secondary conductor D, the face of core B is cutaway, so that air gaps H are formed in the magnetic circuit whichconstitute a permanent reluctance therein.

In the form shown in Fig. 2, the stationary core A has a leg I whichenters the primary coil. The secondary conductor D is applied to saidleg, and the air gaps H are made by cutting away the extremity of saidleg in the manner already described.

In the form shown in Fig. 3, two secondary conductors D and D areemployed, one on the leg I, and the other on the armature B.

In the form shown in Fig. 4, two movable cores or armatures B, B arepresent, each carrying a secondary conductor 1) and D.

Instead of using one secondary conductor, as D, upon either stationaryor movable core, I may use two such conductors J, J, Figs. 7, 8, a partof each conductor being seated. in a milled recess in the end of thecore, so that each conductor surrounds a part of the core.

Instead of making the secondary conductor in the form of a sleeveextending for a short distance into the movable core, I may elongatesaid sleeve to extend as far into said core as may be desired. And I mayform arms K on it projecting beyond the end of the core and beyond theprimary coil, as shown in Fig. 9, to which arms may be connected anymember L, designed to be actuated by the movement of said core.

The secondary circuit conductor is to be given an ohmic resistanceproportioned to the frequency of the current alternations; (he,Q'lt-lflltfl the frequency, the greater be ing the resistance. This maybe accomplished by selecting a suitable metal for the said conductor. Ihave found brass, or even copper, suitable for low frequencies, and

German silver for high ones. It may also be accomplished by suitablyproport-ioning the dimensions of the sleeves. It is important to observealso, that the sleeve should also be proportioned in mass and radiatingsurface, so as to effect proper absorption and distribution of the heatgenerated therein, and that such proportioning is to be considered inadapting the secondaryconductor to the frequencies employed. Extendingthe sleeve into the core increases both mass and radiating surface, andwhere more rapid cooling is desired, making the secondary conductor withprojections extending outside the core, as shown in Fig. 9, facilitatesthat object.

It is preferable to provide the ends of the arms of the core A with afacing M, Fig. 3, of non-magnetic metal, such as brass or copper, so asto provide for a certain permanent reluctance in the magnetic circuit incase of the core B coming in contact with core A, and to prevent contactof iron to iron.

The following arethe actual dimensions of an alternating current magnet,which has been manufactured under my direction for actual commercialuse, the-specific form of core being substantially that shown in Figs. 7and 8. Length of conductors J, J4 inches. MaterialGerman silver, 18%

' nickel, for 60 cycles; soft brass for 25 cy-' cles. Externaldimensions of cross sectional parallelogram; length 1% incheswidth inch.Thickness of conductors inch. Laminations-sheet steel, No. 28 gage, ineach conductor about 20, between conductors about 40. For 220 volts, 6Ocycles, the magnet coil was wound with 500 turns of No. 14 B.- & S. D.C. C. wire with taps at 450, 4:00 and 350 turns. For exactly the abovevoltage the 450 turn tap was used.

. With 192 volts, 60 cycles, the total pull of the magnet was 82 pounds.

I claim:

1. An alternating current electro-magnet comprising a stationary core, amovable core in plunger form, and an abutment for said movable corewithin the magnet coil: one

comprising a primary coil, a stationary core,

a movable core, and a secondary conductor on each of said cores.

5. An alternating current electro-magnet comprising a primary conductor,a core having two recesses in its polar face, and a secondary conductorseated in said recesses and inclosing the intervening portion of saidcore.

6. An alternating current electro-magnet comprising a core, and primaryand secondary circuit conductors, to cause the magnetic fluxes due tothe currents in said conductors to differ in phase: the said secondaryconductor having an extension protruding beyond its supporting core, andthe said conductor and extension being proportioned to absorb anddistribute the heat developed in said secondary conductor.

DAVID L. LllN DQUIST.

\Vitnesses GERTRUDE T. PORTER, MAY T. MCGARRY.

